"Very rarely do I have such an extraordinary pleasure as I have today to welcome three iconic figures, three genuine American heroes," Obama said, adding: "To have Neil Armstrong, Michael Collins, and Buzz Aldrin here beside me is just wonderful."

"The touchstone for excellence in exploration and discovery is always going to be represented by the men of Apollo 11," Obama said.

"Their work sparked innovation, the drive, the entrepreneurship, the creativity back here on Earth."

Obama, marking the historic occasion, said: "I think that all of us recall the moment in which mankind finally was untethered from this planet and was able to explore the stars; the moment in which we had one of our own step on the moon and leave that imprint that is there to this day."

"It is because of the heroism, the calm under pressure, the grace with which these three gentlemen operated, but also the entire NASA family that was able to, at great risk oftentimes, and with great danger, was able to lift our sights, not here in the US but around the world," Obama said.

The president recollected how he watched the historic event sitting on the shoulders of his grandfather. "I grew up in Hawaii and I still recall sitting on my grandfather's shoulders when those capsules would land in the middle of the Pacific and they'd get brought back and we'd go out and we'd pretend like they could see us as we were waving at folks coming home."

"I remember waving American flags and my grandfather telling me that the Apollo mission was an example of how Americans can do anything they put their minds to," he said.

Obama, on the occasion, reiterated his endeavour to make maths and science once again a popular subject in US schools.

"One of the things that I have committed to doing as President is making sure that math and science are cool again, and that we once again keep the goal by 2020 of having the highest college graduation rates of any country on Earth, especially in the maths and science fields," he said.